1870.| ON THE MYOLOGY OF PLATYDACTYLUS JAPONICUS. 413 
6. Notes on the Myology of Platydactylus japonicus. ° 
By Atrrep Sanpers, M.R.C.S., F.Z.8. 
If one may judge from treatises on Comparative Anatomy recently 
published, the muscles of the Lacertilia do not appear to have re- 
ceived a great deal of attention. This consideration has emboldened 
me to lay the following notes on the myology of Platydactylus 
japonicus before the Zoological Society,—the more so as this species 
differs considerably in the arrangement of its muscular system from 
the Iguana tuberculata, the myology of which was described in a 
paper by Mr. St. George Mivart, published in the Society’s Proceed- 
ings in 1867. 
Hyo-mandibular.—On the ventral aspect of the throat are seen 
two superficial skin-muscles, the most anterior of which arises by 
means of a tendinous raphe covering the glosso-hyal, being thus 
united to its fellow of the opposite side; and passing directly outwards 
through the fibres of the mylo-hyoid, it is inserted into the supple- 
mentary or coronoid and opereular pieces of the mandible immediately 
beneath the posterior teeth. 
The next muscle slightly overlaps the last anteriorly, and arises 
from the basihyal at the point where the anterior horns are given off, 
and from a thin aponeurosis over the hyomandibular, and also from 
one covering the trachea behind the same point. As far back as op- 
posite the posterior end of the mandible it is divisible into three 
distinct portions; the posterior passes outwards and upwards, and 
spreads out into a thin layer, which is inserted into the superficial 
fascia at the back of the head, intimately connected with the tra- 
pezius. The anterior portion forms a thin Jayer, covering the external 
pterygoid, and is inserted into the supraangular piece of the mandible; 
its posterior fibres are collected into a thicker mass, which passes 
upwards and rather backwards behind the mandible, and is inserted 
into the aponeurosis of the side of the neck and the complexus. The 
middle portion passes upwards within the mandible, and is inserted 
into the extremity of the terminal segment of the anterior cornu 
(cerato-hyal) of the os hyoides, close to the attachment of the latter 
to the exoccipital. This latter part perhaps represents stylo-hyoid. 
Mylo-hyoid arises from the body of os hyoides (basihyal) and from 
the posterior cornu (thyro-hyal) as far outwards as the external ptery- 
goid, leaving a space through which that muscle passes. The fibres 
run forward, and are inserted into the whole length of the dentary 
piece of the mandible, with the exception of a small portion anteriorly 
close to the symphysis ; it is also attached to the fascia covering the 
anterior point of the glosso-hyal ; it is situated deeper than or above 
the preceding muscular layers. 
Genio-hyo-glossus arises from the posterior cornu of the os hyoides 
just beyond its articulation with the basihyal; and passing forward, 
its superficial fibres are inserted into the symphysis of the mandible, 
while the deeper ones go to the side and back of the tongue; the 
Proc. Zoou. Soc.—1870, No. XXVIII. 
